Holocene History of the East Antarctic Ice Sheet Environmental Magnetic Record from Mac. Robertson Land

• Main Author: Kacperowski, Kenneth R., Jr.
• Format: Text
• Language: unknown
• Published: Montclair State University Digital Commons 2009
• Subjects: Earth Sciences; Environmental Sciences; Antarctic; East Antarctic Ice Sheet; Mac. Robertson Land; Mac.Robertson Land; Antarc*; Ice Sheet; Mac Robertson Land; United States Antarctic Program
• Online Access: https://digitalcommons.montclair.edu/etd/1174; https://digitalcommons.montclair.edu/context/etd/article/2176/viewcontent/Kacperowski_Thesis_2009_Redacted.pdf

A 24-m jumbo-piston core containing a 14 ka Holocene-Late Pleistocene sedimentary record was collected from Mac.Robertson Land during United States Antarctic Program cruise NBP01-01. This study uses environmental magnetism to trace the Holocene history of the East Antarctic Ice Sheet (EAIS), which is generally thought of as stable since it is grounded above sea level. Magnetic analyses are used to identify periods of terrigenous sedimentation from the EAIS, for example ice rafted debris layers or meltwater pulses. Terrigenous material contains magnetic minerals, which we expect to stand out from the dominantly biosiliceous sediment deposited along the East Antarctic Margin. Magnetic susceptibility is weak down core (approximately -2 to 5 *10-8 m3/kg) until approximately 10.0 ka where there is a steep increase in intensity, most likely due to sandy mud laminae and underlying diamict. Analysis of X-rays down core show periods of high and low frequency of laminations down core, until a varved layer stratigraphically above the diamict (5-16 laminations per 5 cm). Gravel grains are sparsely present down core until the diamict, where they are ubiquitous. These changes in lithology represent déglaciation following the last glacial maximum and the transition to an open marine environment at 14 ka. Based on ARM and SIRM data, the upper core (0.8-7.7 ka) exhibits a low abundance of magnetic material until approximately 7.7 ka, where there is an increase in fine magnetic material above the background until 10.4 ka. Magnetic assemblages for the upper core (approximately 0.8-9.0 ka) likely consist of magnetite and titanomagnetite based upon SIRM/X and S-ratio values of 0.1 - 12 kA/m and 0.9- 0.95, respectively (Evans and Heller, 1999). The assemblage changes in the lower core (prior to 9.0 ka) with isolated peaks in SIRM/X suggesting magnetic iron sulfites (greigite and pyrrhotite) and also the presence of high coercivity minerals such as hematite and goethite. From 0.8 to 4.4 ka, ARM exhibits a zone of regularly spaced ...